Touch-responsive tone envelope control circuit for electronic musical instruments

ABSTRACT

In a keying system for an electronic musical instrument in which an individual keyer is adapted to be controlled in response to the intensity of depression of a corresponding playing key so that a keyed tone signal has an amplitude in accordance with the key depression intensity, a common DC supply means with a voltage selector is provided to additively control the keyer irresponsive to the key depression intensity. The voltage selector determines which one of said two controls should prevail. The system is simple in construction and operation and inexpensive and easy to manufacture as well as provides a variety of excellent tonal effects.

United States Patent TOUCH-RESPONSIVE TONE ENVELOPE CONTROL CIRCUIT FORELECTRONIC MUSICAL INSTRUMENTS 10 Claims, 3 Drawing Figs.

US. Cl 84/l.0l, 84/l.l3, 84/].26

Int. Cl Gl0h 1/00 Field of Search 84/1 .01

Primary Examiner-Thomas .l. Kozma Assistant Examiner-U. WeldonA!t0meyCushman, Darby & Cushman ABSTRACT: In a keying system for anelectronic musical instrument in which an individual keyer is adapted tobe controlled in response to the intensity of depression of acorresponding playing key so that a keyed tone signal has an amplitudein accordance with the key depression intensity, a common DC supplymeans with a voltage selector is provided to additively control thekeyer irresponsive to the key depression intensity. The voltage selectordetermines which one of said two controls should prevail. The system issimple in construction and operation and inexpensive and easy tomanufacture as well as provides a variety of excellent tonal effects.

TOUCH-RESPONSIVE TONE ENVELOPE CONTROL CIRCUIT FOR ELECTRONIC MUSICALINSTRUMENTS The present invention relates to a touch-responsive toneenvelope control circuit for electronic musical instruments, and moreparticularly, to a specific tone envelope control circuit which canimprove the tone envelope effects in a keyoperated electronic musicalinstrument such as an electronic organ to provide excellent effects ofmusic being played.

It, therefore, is the principal object of thepresent invention toprovide a tone envelope control circuit which is simple in construction,and easy and inexpensive to manufacture and which permits the electronicmusical instrument incorporating the circuit to provide a variety ofexcellent tonal effects by making use of the efi'ect that the toneenvelope is subjected to the intensity of a playing key depression,called a touchresponsive control effect."

According to the present invention, there is provided a combination of aplurality of keyer circuits and a circuit connected through a manualchangeover switch and allowing the keyer circuits to providea loud tonesignal having a predetermined large amplitude regardless of theintensity of key depression while providing a soft tone signal having apredetermined small amplitude when the intensity of the key depressionis very low, so that the player can easily provide various kinds ofkeying effects at will.

Other objects, features and advantages of the present invention will beapparent from the following detailed description taken in conjunctionwith the accompanying drawings in which,

FIG. 1 is a circuit diagram showing an embodiment of the presentinvention,

FIGS. 2 and 3 are partial circuit diagrams showing modifications of theessential portion of the embodiment of FIG. 1.

The same characters or references are hereafter used to indicate thesame parts.

Reference is made in detail to a preferred embodiment of the presentinvention with reference to the accompanying drawings.

L designates a coil grounded at one end thereof and adapted" to vary theinterlinking fluxes in association with depression of an operating keyarranged on a keyboard of an electronic musical instrument (eg the keycarries a magnet thereunder), the other end of which is grounded througha series circuit of a rectifying element D and a capacitor C. A junctiond between the element D and the capacitor C is connected to a movablecontact SA, of a changeover switch SA of one-pole two-position type,which is actuated in association with the operation of the key K. Theconnection point d is also connected respectively through resistors R,and R to the gates of field effect transistors Q, and Q (hereunderreferred to as FETs) between whose sources series connected resistors Rand R, are connected. The connection point r,, of the resistors connectswith the juncture r,,, of bleeder resistance elements R and R connectedin series between a DC voltage +Vcc of a power source and ground. Thejuncture r,,, is also grounded via a capacitor C,,.

The sources of the FET's Q, and Q, are adapted to receive throughterminals t, and individual tone signals each having a predeterminedfrequency of different footage, produced by conventional tone generatorsof the electronic musical instrument (not shown), respectively. At thedrains of the FETs Q, and Q load resistors R, and R, connected to thepower voltage +Vcc at their one ends are connected at the other ends,respectively. At the connection points of the drains of the FETs Q, andQ and the load resistors are provided respectively output terminals T,and T which are adapted to develop the tone signals each having arequired envelope (amplitude) and a different footage number applied tothe input terminals t, and from the respective drains thereof by varyingthe gate potentials at the FETs Q, and Q in association with theoperation of the key. As a whole, the above-mentioned arrangements areshown as a key depressing speed detecting circuit S, and a keyer circuit8 by two two-dot chain blocks in FIG. 1.

In the detecting circuit 8,, one stationary contact SA, (normallyclosed) of the circuit changeover switch SA is grounded via a resistor Rand the other stationary contact SA, (normally open) is connectedthrough a unidirectional conducting element D,, such as a diode to amovable contact SB, of onepole three-position type changeover switch SB,which may be manually operated and is used in common to the whole keyingcircuit in the electronic musical instruments. One stationary contactSB, of the switch SB is grounded, while other stationary contacts SB,and SB; respectively are connected to r and r, which are connectionpoints between series-connected bleeder resistors R,,, R, and R,,connected between the power voltage +Vcc and ground. The movable contactSB, is connected to a common line 1,, to which the indicated D and allthe other D s in other detecting circuits (not shown) are connected.

The keyer circuit S is so constructed that the gate-to-source potentialof each FETs Q, and Q, is set through the resistors R and R at such arequired value that when each of the gate potentials is at an earthpotential, i.e., 0 volts, each of the FET's is caused to benonconducting so that the drain-source impedance is rendered extremelyhigh. The movable contact SA, of the changeover switch SA provided inthe detecting cir cuit S, is arranged to contact the stationary contactSA, only when the key is depressed. The number of the detecting circuitsS, and the keyer circuits S which are installed in the console of theelectronic musical instrument corresponds in number to the playing keys,for example, 61. Now, it is to be notedthat the changeover switch SB maybe of one-pole twoposition type in case either of SB, contact and SB,contact is not required in design.

Now, description will be made on the operation of the above-mentionedcircuit arrangement.

At first, under a condition that the movable contact SB, of the circuitchangeover switch SB is contacted by the contact 5B,, when any one key Kprovided in the electronic musical instrument is depressed, a magneticmember attached to the key moves close to or away from a fixed coil L,thereby resulting in a damped pulse voltage approximately proportionalto the intensity of speed of depression of a playing key due to avariation in interlinking fluxes established round the coil. The inducedalternative voltage is rectified through the element D and as a result,a positive DC voltage developed at the element D is stored in thecapacitor As soon as the charge stored on the capacitor C is appliedrespectively through the resistors R, and R, to the gates of the FETs Q,and 0,, the respective drain-source impedances are caused to be reducedin response to the gate input levels of the F ETs, so that theindividual tone signals applied to the sources of the FETs may bederived at the output terminals T, and T 2 provided at the drain sidethereof. At this time, since the movable contact SA is actuated ininterlocked relation with the operation of the key K, namely, since thecontact SA, is made in contact with the stationary contact SA, onlyduring depression of the key as shown by a dotted line in FIG. 1, thepositive charge stored on the capacitor C is blocked by a reverselyconnected diode D to flow in the common line I,,, thus, no discharge iscaused, and hence, the charge is applied through resistors R, and R tothe gates of the FETs Q, and Q resulting in reduction of thesource-drain impedance of each of the F ET's in response to theintensity of key depression as mentioned above. As a result, the toneinput signals separately applied to the respective sources of the FETsmay be derived at the output terminals T, and T which are on the drainside of the FETs separately. The envelope (amplitude) of the output tonesignal varies in response to the intensity or speed of the keydepression. That is, upon quick depression of key, the charge stored onthe capacitor C provides a high potential, causing an output tone signalof a high level, while with slow depression of key, the output tonesignal may be obtained at a low level. Thus, the present arrangementpermits a tone envelope control which provides a so-calledtouch-responsive effect in an electronic musical instrument and whichprovides said effect resembling that of a piano.

ln the case described above, if the playing key K is kept depressed, nofurther alternating voltage is induced in the coil L. However, since theinput gate impedance of each of the FETs Q, and Q, is very high (forexample, l ohms) the charge stored on the capacitor C immediately afterdepression of the key has no discharging path, and accordingly, it doesnot discharge for a long period of time, so that the F ETs Q, and Q, areheld in their conducting states during the depression of the key, ateach of terminals T, and T continuously providing the output tone signalhaving a level responsive to the intensity of the key depression.

Upon release of the key being depressed, the key is made restored by itsself-return action and simultaneously, the movable contact SA, of thechangeover switch SA is also returned to be in contact with the contactSA, at the position as shown by a solid line in FIG. 1, so that thecharge stored on the capacitor C discharges in a short period of timethrough the resistor R,, having a relatively low resistance.Accordingly, the gate potential of each of the FETs Q, and Q becomes theearth potential, i.e., 0 volts to render the FET's Q, and O to be intheir nonconducting states, so that no output signal is developed atboth terminals T, and T Now, considering the case where the playing keyK is quite slowly depressed, voltage induced in the coil L is too small,and as a result, there will occur the case where the gate of each of theFETs Q, and 0, cannot be at a positive voltage sufficient to beconductive between the source and the drain. Further, there is apossibility of producing no output even though the key is depresseddepending upon the intensity of key depression, and hence, the player isrequired to be skillful in playing the instrument in order to producedesired soft tones without fail, resulting in nervous strain.

On the contrary, when the electronic musical instrument is played at aloud tone level the key K is always required to be quickly and stronglydepressed, and a long play under such a condition results in the fatigueof the player. In the present invention, various attempts have been madeto obviate these conventional defects. The bleeder resistors R,,, R,,,and R,, are arranged to divide the power voltage +Vcc at a predeterminedratio, and a positive voltage V, appearing at the connection point r, isset at substantially the same as the charged voltage across thecapacitor C when the intensity of key depression is weak. That is, incase any one key is too slowly depressed under the state in which themovable contact SE, is in contact with the stationary contact 88 theinduced voltage in the coil L will be too small and the voltage V, willprevail to be applied to the capacitor C for charging it via theunidirectional conducting element D and the movable contact SA, being incontact with the contact SA, by key depression. The voltage V, is alsoapplied respectively through the resistors R, and R to the respectivegates of the FETs Q, and 0,. As a result, the source-drain impedance ofeach PET is lowered to some limited extent, so that input tone signalsof different footage number which are separately applied to therespective sources thereof can surely be derived separately at theterminals T, and T, on the drain side thereof as output tone signalswith low levels. That is, since the voltage V, at the connection pointr,, is set substantially the same as the storage voltage of thecapacitor C upon weak key depression, even an extremely slow keydepression permits soft tone to be produced with the help of the voltageV,. Therefore, the above arrangement facilitates the soft tone producingplay as well as a long playing, and the nerve strain of the player isgreatly reduced. In this case, release of the depressed key allows boththe key and the changeover switch SA to return to their initial state,and allows the charge stored on the charged capacitor C to be dischargedin a short period of time via the resistor R,,, so that each FET isturned to its nonconducting state to shut off any output signals.

The bleeder resistors R,,, R,,, and R,, serve to divide the powervoltage +Vcc at a predetermined ratio to provide a positive voltage V,at the connection point r,. The voltage V, is determined to besubstantially the same as the charged voltage across the capacitor Cupon key depression with a high intensity. Therefore, in case keydepression is effected under the condition in which the movable contactSB of the changeover switch SB is in contact with the stationary contact88 the voltage V is always greater than the induced voltage in the coilL and is applied-via the unidirectional conducting element D, and themovable contact SA which, by key depression, is brought into contactwith the contact SA to the capacitor C for charging it, and is alsoapplied respectively via resistors R, and R to the gates of the FETs Q,and 0,, so that the source-drain impedances thereof are extremelyreduced to allow the output terminals T, and T separately to derivedesired output tone signals irrespective of the intensity of keydepression.

This can be explained as follows. That is, since the voltage V: at thepoint r, is substantially the same as the charged voltage across thecapacitor C when the intensity of key depression is high, loudtone-producing play on the electronic musical instruments can beperformed independently of the intensity of key depression. For example,even if the player slowly depresses the key K, such loud tone-producingplay becomes possible. The operational manner in the circuit uponrelease of the depressed key is the same as described above. This willbe convenient, when the player wants to play the entire music loudly.

Further, as the manual changeover switch SE, a one-pole two-positiontype switch may be employed. Another embodiment using a switch of thistype is shown in FIG. 2, in which a series circuit of a bleeder resistorR,,, a potentiometer R and a resistor R,, is connected between the powervoltage +Vcc and ground, the stationary contact 88 is connected to amovable contact r of the potentiometer R, whereby the whole toneenvelopes in soft or loud tone generating play by key depressingoperation can be varied by changing the dividing voltage ratio byadjustment of the slidable contact r, Further, if there is provided anarrangement that the common line 1,, is connected directly to a slidablecontact r,;, of a potentiometer R as shown in FIG. 3, theabove-mentioned actions such as variations in tone levels or envelopes,etc. can be performed without using the changeover switch SB.

As the key depression speed detecting circuit 8,, magnetosensitiveelements or pressure-sensitive elements may be used in place of theinduction coil used here. Furthermore, the FETs used in the keyercircuit may be substituted by other switching elements such astransistors, diodes or vacuum tubes etc.

lclaim:

1. In an electronic musical instrument having a plurality of keys, atouch-responsive keying system comprising:

a plurality of touch-responsive means, each for generating atouch-responsive DC voltage that corresponds to an intensity ofdepression of a respectively associated one of said playing keys,

a plurality of charge storage elements, one being provided and connectedto each of said touch-responsive means for storing said touch-responsiveDC voltage,

a plurality of keyer circuits, each corresponding to one of said chargestorage elements and having a control terminal connected thereto,

a plurality of diodes, one being provided for each of said means,

voltage supply means for providing a predetermined DC voltage, means forconnecting said predetermined DC voltage to said plurality of diodes,and

connecting means at each keyer circuit responsive to the depression ofan associated key for connecting said predetermined DC voltage through acorresponding one of said diodes to a respectively associated controlterminal thereby permitting said predetermined DC voltage to be suppliedto a control terminal when said predetermined voltage is greater thansaid touch-responsive DC voltage for a particular key.

2. A touch-responsive keying system according to claim 1,

in which each of said charge storage elements is connected to adischarge element when its associated key is not fully depressed.

3. A touch-responsive keying system according to claim 1, in which saidpredetermined DC voltage is substantially equal to the touch-responsiveDC voltage generated and stored by a weak key depression intensity.

4. A touch-responsive keying system according to claim 1, in which saidpredetermined DC voltage is substantially equal to the touch-responsiveDC voltage generated and stored by a strong key depression intensity.

5. A touch-responsive keying system according to claim 1, in which thereare provided two voltage supply means, one of which provides apredetermined DC voltage substantially equal to the touch-responsive DCvoltage generated and stored by a weak key depression intensity and theother of which provides a predetermined DC voltage substantially equalto the touch-responsive DC voltage generated and stored by a strong keydepression intensity, and means for selecting either one of said twopredetermined DC voltages for connection to a respectively correspondingcontrol terminal.

6. A touch-sensitive keying system for an electronic musical instrumentcomprising a plurality of individual key actuated circuits, each having:

a coil adapted to generate an induced electromotive force responsive tothe actuation speed of a playing key,

a capacitor efiectively connected to said coil for storing the inducedelectromotive force,

a discharging resistor,

a key-actuated changeover switch, one fixed contact of the changeoverswitch being connected to said resistor for effecting an electricalconnection of said resistor across said capacitor during release of anassociated key and another fixed contact of the changeover switch beingconnected to a unidirectional conducting element,

a keyer circuit, having a control terminal connected to said capacitor,for controlling the output characteristics of the musical instrument inassociation with the intensity of depression of the individual playingkey by applying an input to said control terminal of the keyer circuitwith the charge stored on the capacitor, and

a supply means connected to the unidirectional conducting element forsupplying a preselected DC voltage to the control terminal upon fulldepression of the key via said changeover switch whereby saidpreselected DC voltage is supplied to the control terminal if it isgreater than the voltage stored in said capacitor.

7. A touch-sensitive keying system according to claim 6, in which saidkeyer circuit includes:

a pair of active elements, each having a control electrode, a

cathode electrode and an anode electrode,

a pair of input and output terminals,

each of said control electrodes being commonly connected via a separateresistor to the capacitor,

each of said cathode electrodes being connected to an individual inputterminal for receiving an input tone signal of difierent footages, and

each of said anode electrodes being connected to an individual outputterminal to derive the output signal thereat through an individual load.

8. A touch-responsive keying system according to claim 7, in which saidactive elements are field effect transistors.

9. A touch-responsive keying system according to claim 6, in which saidvoltage supply means includes a voltage divider and a voltage selectingswitch combined therewith.

10. A touch-responsive keying system according to claim 6 in which saidvoltage supply means includes a potentiometer to permit continuouspreselection of a DC voltage to said control terminal.

1. In an electronic musical instrument having a plurality of keys, atouch-responsive keying system comprising: a plurality oftouch-responsive means, each for generating a touch-responsive DCvoltage that corresponds to an intensity of depression of a respectivelyassociated one of said playing keys, a plurality of charge storageelements, one being provided and connected to each of saidtouch-responsive means for storing said touch-responsive DC voltage, aplurality of keyer circuits, each corresponding to one of said chargestorage elements and having a control terminal connected thereto, aplurality of diodes, one being provided for each of said means, voltagesupply means for providing a predetermined DC voltage, means forconnecting said predetermined DC voltage to said plurality of diodes,and connecting means at each keyer circuit responsive to the depressionof an associated key for connecting said predetermined DC voltagethrough a corresponding one of said diodes to a respectively associatedcontrol terminal thereby permitting said predetermined DC voltage to besupplied to a control terminal when said predetermined voltage isgreater than said touch-responsive DC voltage for a particular key.
 2. Atouch-responsive keying system according to claim 1, in which each ofsaid charge storage elements is connected to a discharge element whenits associated key is not fully depressed.
 3. A touch-responsive keyingsystem according to claim 1, in which said predetermined DC voltage issubstantially equal to the touch-responsive DC voltage generated andstored by a weak key depression intensity.
 4. A touch-responsive keyingsystem according to claim 1, in which sAid predetermined DC voltage issubstantially equal to the touch-responsive DC voltage generated andstored by a strong key depression intensity.
 5. A touch-responsivekeying system according to claim 1, in which there are provided twovoltage supply means, one of which provides a predetermined DC voltagesubstantially equal to the touch-responsive DC voltage generated andstored by a weak key depression intensity and the other of whichprovides a predetermined DC voltage substantially equal to thetouch-responsive DC voltage generated and stored by a strong keydepression intensity, and means for selecting either one of said twopredetermined DC voltages for connection to a respectively correspondingcontrol terminal.
 6. A touch-sensitive keying system for an electronicmusical instrument comprising a plurality of individual key actuatedcircuits, each having: a coil adapted to generate an inducedelectromotive force responsive to the actuation speed of a playing key,a capacitor effectively connected to said coil for storing the inducedelectromotive force, a discharging resistor, a key-actuated changeoverswitch, one fixed contact of the changeover switch being connected tosaid resistor for effecting an electrical connection of said resistoracross said capacitor during release of an associated key and anotherfixed contact of the changeover switch being connected to aunidirectional conducting element, a keyer circuit, having a controlterminal connected to said capacitor, for controlling the outputcharacteristics of the musical instrument in association with theintensity of depression of the individual playing key by applying aninput to said control terminal of the keyer circuit with the chargestored on the capacitor; and a voltage supply means connected to theunidirectional conducting element for supplying a preselected DC voltageto the control terminal upon full depression of the key via saidchangeover switch whereby said preselected DC voltage is supplied to thecontrol terminal if it is greater than the voltage stored in saidcapacitor.
 7. A touch-sensitive keying system according to claim 6, inwhich said keyer circuit includes: a pair of active elements, eachhaving a control electrode, a cathode electrode and an anode electrode,a pair of input and output terminals, each of said control electrodesbeing commonly connected via a separate resistor to the capacitor, eachof said cathode electrodes being connected to an individual inputterminal for receiving an input tone signal of different footages, andeach of said anode electrodes being connected to an individual outputterminal to derive the output signal thereat through an individual load.8. A touch-responsive keying system according to claim 7, in which saidactive elements are field effect transistors.
 9. A touch-responsivekeying system according to claim 6, in which said voltage supply meansincludes a voltage divider and a voltage selecting switch combinedtherewith.
 10. A touch-responsive keying system according to claim 6 inwhich said voltage supply means includes a potentiometer to permitcontinuous preselection of a DC voltage to said control terminal.